1. Field of the Invention
The present invention relates generally to an improved rotary valve and more particularly to an improved rotary valve appropriately providing an intake and exhaust valve for internal-combustion engines, e.g., gasoline engines and diesel engines.
2. Description of the Related Art
Prior-art intake and exhaust valves of four-cycle internal-combustion engines which have been provided until now are classified into the following categories: a first form including a valve body which rises perpendicularly from its seat and falls perpendicularly thereon and a second form including a valve body which is in sliding contact with its seat within a valve casing. The first form of the intake and exhaust valves is a poppet valve. The second form comprises a sleeve valve including a sleeve-shaped valve body slidably mounted within engine cylinder and a rotary valve including a valve body which is slidably rotatably mounted within a seat.
At the present time, a poppet valve is predominantly used for intake and exhaust valves of four-cycle gasoline engines. Since the poppet valve has a high sealability, high lubricatability and high reliability, it is predominantly used for practical intake and exhaust valves of an automotive internal-combustion engine. However, the poppet valve is not always suitable for use in a high-speed internal-combustion engine. A camshaft driven poppet valve presently tends to be predominantly used in an internal-combustion engine for passenger car. The camshaft driven poppet valve is yet limited so that a use of it may result in a rapid reduction in engine volumetric efficiency or a destruction of the high-speed engine in an extreme case.
In detail, since the camshaft driven poppet valve is a relatively low rigid, elastic system, a resonance of one of normal vibrations of this system with one of harmonic components of a camming force exerted by the camshaft may cause the operational sequence of the system to be irregular so that a component of the poppet valve jumps and a valve spring exerting its force on the poppet goes out of its normal operation to a surging. An engine in such state produces a high noise, causes the operational timing of the poppet to go out of order and rapidly reduces its power.
Thus, the camshaft driven poppet valve develops the above problems because of its constitution as engine speed increases. In order to overcome the problems in the camshaft driven poppet valve, various non-poppet valves have been proposed and experimentally manufactured. However, all developments of these non-poppet valves have failed and nothing of the various non-poppet valves has been yet realized.
First, a lift valve of the non-poppet valves fails to fit high-speed engine, entails a complication in an operating mechanism for a valve body and produces much noise and low antiknock quality on engine.
Second, the sleeve valve, one form of slide valves, produces a high antiknock quality on engine and includes an operating mechanism for the sleeve more simplified in structure than the operating mechanism for a poppet of the poppet valve. The sleeve valve entails problems in a heat exhaust and a lubrication so that it fails to fit high-speed engine. The sleeve valve also produces an unsatisfactory noise.
Rotary valves are classified into a plurality of categories in accordance with configurations of rotors and arrangements of passages for combustible gas or air and exhaust gas. Since a prior-art intake and exhaust rotary valve includes in principle a rotor revolving at a uniform speed in sliding contact with a seat surface having open edges of intake and exhaust and a combustion chamber to periodically open and shut communications of the intake and the exhaust and combustion chamber, it is best appropriate to a high-speed engine. In particular, it provides a greater opening speed in the communications of the intake and the exhaust and combustion chamber than the poppet valve.
The following drawbacks seem to have blocked an actual use of the rotary valve as the intake and exhaust valve for automotive engine until now although the rotary valve has the above advantages: (i) The rotary valves have a poor sealability in principle. (ii) Therefore, providing a means for pushing the rotor on a seat surface in order to improve the sealability of the rotary valve impairs a smooth operation of the rotor to deteriorate the essential advantages of the rotary valve. In other words, the rotor must smoothly revolve and produce a low friction and low wear, and a lubricating oil consumption of the rotary valve must be low.
FIG. 12 illustrates a Minerva (a motorcar manufacturing corporation in Belgium) type rotary valve. The cylindrical surface of a rotor indicated at 50 has indentations 51a, 51b and 51c. In accordance with the FIG. 12 position of the rotary valve, two lands adjoining the circumferentially opposite edges of the indentation 51c shut a combustion chamber 52 from an intake 53 and an exhaust 54. A rotor 50 further goes from the FIG. 12 position in the direction of the arrow A to open the combustion chamber 52 to the intake 53. Then, a further rotation of the rotor 50 shuts the combustion chamber 52 from the intake 53 while a combustion is performed within the combustion chamber 52. Then, a further rotation of the rotor 50 enables the indentation 51b to open the combustion chamber 52 to the exhaust 54 to exhaust the combustion chamber 52.
FIG. 13 illustrates a sealing arrangement of the FIG. 12 rotary valve. This sealing arrangement comprises a wedge 56 positionally controlled by a control assembly including a screw 55. As seen in FIG. 13, a rightward movement of the wedge 56 more forcibly urges the rotor 50 on sliding-contact surfaces 55a and 55b of a cylinder block through the retainer 57 to better seal the open edge of the exhaust 54 in the seat contact surfaces 55a and the top open edge of the combustion chamber 52 in the sliding-contact surfaces 55b.
In accordance with the Minerva-type rotary valve, a relatively large contact surface area between the cylindrical surface of the rotor and sliding-contact surfaces and an increased contact pressure of the rotor on the sliding-contact surfaces secure the sealability of the rotary valve, so that a frictional resistance to the rotor is large and a lubrication for the rotor entails a problem to greatly reduce the essential advantages of the rotary valve. That is, an increase in the sealability and a reduction in the frictional resistance are in an opposite relation so that a reduced frictional resistance to the rotor reduces the sealability of the rotary valve and on the other hand, an increased sealability of the rotary valve increases the frictional resistance to the rotor.
Since the contact pressure of the rotor is constant and sufficiently large to secure the sealability of the rotary valve when an engine receives a maximum load, it causes a high frictional resistance to the rotor when the engine receives a low load so that the rotor slowly rotates.
A Baer type sleeve-shaped rotary valve and a flat-rotor type rotary valve assembly realized in United Kingdom in 1930 in which a perforated flat integral rotor is arranged within each of intake and exhaust passages for engine cylinders and rotates to perform intake and exhaust strokes of the engine cylinders were proposed. These rotary valves entailed essentially the same drawbacks as the Minerva type rotary valve and failed to be actually used. As understood from the above, the most important problem in the rotary valve is to secure the sealability.